The present invention relates to a plasma processing apparatus used for etching or ashing when manufacturing a semiconductor device, a liquid crystal substrate, or the like, and for processing an object to be processed, such as a semiconductor wafer or the like, with use of an active species prepared by plasma generation.
FIG. 34 is a view showing a microwave excitation plasma processing apparatus.
An opening portion 2 is formed in the upper surface of a cylindrical air-tight chamber 1. The opening portion 2 is provided with a dielectric window 3 which encloses the air-tight chamber 1. The dielectric window 3 is made of, for example, alumina, quartz glass, and is arranged in the periphery of the opening portion 2, such that the window 3 is in almost the same plane as the uppermost portion of the air-tight chamber 1.
A rectangular microwave guide 4 is provided on the upper surface of the air-tight chamber 1 with the dielectric window 3 inserted therebetween.
The microwave guide 4 serves to introduce a microwave 5 into the air-tight chamber 1, and is provided on the upper wall portion of the air-tight chamber 1 including the dielectric window 3.
A microwave guide port 6 is opened in a bottom plate portion of the microwave guide 4 which is opposed to the dielectric window 3.
A radiation plate 7 made of mesh punched metal is arranged in the horizontal direction in the air-tight chamber 1, so that the inside of the air-tight chamber 1 is divided into upper and lower portions. Specifically, in the air-tight chamber 1, a plasma generation chamber 8 is formed in the upper side while a processing chamber 9 is formed in the lower side.
A gas supply tube 10 is connected to the side wall of the plasma generation chamber 8.
The processing chamber 9 is provided with a shaft 11, and the shaft 11 is equipped with a wafer holder 12.
The bottom portion of the processing chamber 9 is equipped with an exhausting tube 13. Another end of the exhausting tube 13 is connected with an exhausting system 14.
Explanation will now be made of a method for removing (or ashing) a resist pattern on a semiconductor wafer by the apparatus as described above.
At first, a semiconductor wafer 15 is set on the wafer holder 12 of the processing chamber 9 at the lower portion of the air-tight chamber 1. A resist pattern is formed on the semiconductor wafer 15.
A gas in the air-tight chamber 1 is exhausted through an exhausting tube 13 by operating a vacuum pump of an exhausting system 14.
Meanwhile, a plasma generation chamber 8 in the upper power of the air-tight chamber 1 is supplied with a reaction gas, such as an oxygen gas, through a gas supply tube 10.
At the time point when the internal pressure of the air-tight chamber 1 reaches a predetermined pressure by the supply of a reaction gas, a microwave 5 is supplied to the microwave guide 4. This microwave 5 is introduced through the microwave guide 4, passing through the dielectric window 3 from the microwave guide port 6, into the plasma generation chamber 8.
When a reaction gas is thus supplied to the plasma generation chamber 8 and a microwave 5 is introduced, a plasma 16 is generated in the plasma generation chamber 3. Active species, such as active oxygen atoms and ions, are generated in the plasma 16.
The active species are introduced into the processing chamber 9 through an opening in a radiation plate 7. In the chamber 9 the active species react with the surface of a semiconductor wafer 15 in the processing chamber 9, thereby removing the resist pattern. Thus, so-called ashing is performed.
In the apparatus as described above, a heat generated by a plasma 16 transfers to the dielectric window 3, thereby heating the dielectric window. The heat of the dielectric window 3 is radiated by natural cooling.
However, since high speed processing is carried out, the heat amount received from a plasma 16 generated in the plasma generation chamber 8 is increased as the power of the microwave 5 introduced into the microwave introducing tube 4 is increased. In this manner, the temperature of the dielectric window 3 increases to about 400.degree. C., resulting in a possibility that a heat break-down may occur.
A technique for preventing a heat break-down of the dielectric window 3 is taught, for example, in Japanese Patent Application KOKAI Publication No. 63-130784. This reference teaches that an air supply tube 17 is provided at an upper portion of a microwave introducing tube 4, as shown in FIG. 35.
In this structure, the dielectric window 3 heated in accordance with generation of a plasma 16 is forcedly cooled by blowing an air to the dielectric window 3 through the air supply tube 17 from the microwave introducing tube 4.
However, in order to prevent a heat break-down of the dielectric window 3, an enormous amount of air must be blown to the dielectric window 3 through the air supply tube 17.
For example, in a microwave processing apparatus including a dielectric window 3 having a diameter of 240 mm, when a microwave 5 of 1 kW is introduced into the microwave introducing tube, an air of a flow amount of 200 Nl/min or more must be blown to the dielectric window 3 from the air supply tube 17 in order to prevent a heat break-down of the dielectric window 3, so that only low practical utility can be attained.
In addition, if a large amount of air is supplied into the microwave introducing tube 4, an efficiency of plasma generation by a microwave 5 introduced from the microwave introducing tube 4 is lowered.